Background work process on Hold

Dear experts,

I have experienced this many times, I want to clarify with you all.

Frequently in our system a background process in stopped state in SM66. But in SM50 I see they are in HOLD state for X number of seconds (ARFC, RFC). when I looked at developer trace, or job log no errors. In dev trace, there is no update for the time WP is on hold.

Can you please suggest on effective ways to debug a background job which is hold.